Add an example

example.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"flag"
+	"io"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/ericyan/shield/transport/udp"
+	"github.com/ericyan/shield/tuntap"
+)
+
+func main() {
+	bind := flag.String("bind", "0.0.0.0:1984", "ip and port to bind")
+	peer := flag.String("peer", "", "ip and port of the peer")
+	ip := flag.String("ip", "172.16.0.1/31", "ip of the tun device (in CIDR)")
+	mtu := flag.Int("mtu", 1350, "MTU of the tun device")
+	bufsize := flag.Int("bufsize", 1500, "size of the buffer")
+	flag.Parse()
+
+	// Set up the TUN device
+	tun, err := tuntap.NewTUN()
+	if err != nil {
+		log.Fatal(err)
+	}
+	tun.SetMTU(*mtu)
+	addr, err := tuntap.ParseCIDR(*ip)
+	if err != nil {
+		log.Fatal(err)
+	}
+	tun.AddAddr(addr)
+	tun.Up()
+
+	// Set up the UDP transport
+	udp, err := udp.New(*bind, *peer)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Anything received from UDP goes to TUN
+	go func() {
+		buf := make([]byte, *bufsize)
+		_, err := io.CopyBuffer(tun, udp, buf)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	// Anything received from TUN goes to UDP
+	go func() {
+		buf := make([]byte, *bufsize)
+		_, err := io.CopyBuffer(udp, tun, buf)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	log.Printf("Listening on %s with peer %s", udp.LocalAddr(), udp.RemoteAddr())
+	addrs, err := tun.Addrs()
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Printf("%s: %v", tun.Attrs().Name, addrs)
+
+	sig := make(chan os.Signal)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	s := <-sig
+	log.Fatalf("Signal (%v) received, stopping\n", s)
+}